How to Program the Key FOB on a 2003 Chevy Trailblazerby Leonardo R. Grabkowski
The 2003 Chevy Trailblazer came standard with a remote keyless entry fob. You can use this fob to unlock and lock your Trailblazer's doors. After replacing the remote fob's battery, you might need to resynchronize the remote to the Trailblazer by reprogramming it. You might also need to program a remote if you've lost the original. Only a remote key fob specifically made for the Trailblazer will synchronize with the vehicle. The best place to obtain this remote is at a Chevrolet dealership.
Shut your Trailblazer's doors. Put your key in the ignition. Don't turn the key.
Push the "Unlock" switch on the door. Hold the button down.
Turn the key rapidly through the following sequence: "On," "Off," "On," "Off."
Release the "Unlock" switch. At this time, you'll hear the door locks cycle.
Press the "Unlock" and "Lock" buttons on the remote at the same time. Hold the buttons down for up to 30 seconds, or until the door locks cycle again. This remote is programmed to the Trailblazer. If you need to program a spare, hold the "Lock" and "Unlock" buttons on it as well. Turn the ignition to "On" then back to "Off."